We are really only starting to develop the energy potential of the giant nuclear reactor in space that we call the sun. We know that every day it sends enough energy to earth to power human civilization 10 times over, but we haven’t managed to scale ways to harvest it the way nature has done almost perfectly.

For generating electricity, photovoltaic cells on solar panels have been the method of choice, but even then there are different approaches, like large solar farms owned by electric utilities and investors or distributed solar installations on rooftops owned by homeowners and businesses. The latter has been an attractive solution to many: it decentralizes energy production and enables homeowners to get the direct benefits of solar energy.

But the question of scaling remains: how many houses and buildings can realistically benefit from solar? A study by the National Renewable Energy Laboratory (NREL) tried to answer just that, and came to the conclusion that about 25% of the electricity needs in the US could come directly from rooftop solar installations.

Whether a rooftop is suitable for a solar installation depends on a lot of factors, including the amount of average sunlight in the region, the amount of direct sunlight that hits the roof based on its environment (e.g. trees and surrounding buildings), among other things.

NREL performed an extensive study by gathering geospatial data, including light detection and ranging (lidar) data, geographic information system (GIS) methods, and used statistical analysis to determine what percentage of rooftops could realistically be suitable for solar installations.

The research team used the data to project the electricity generation of those rooftop solar installations and came to the conclusion that they could produce 1,118 gigawatts (GW) of power. The study, which was published earlier this year and is embedded in full below, shows a significant increase in potential from the previous similar study performed in 2008 (664GW – 800 TWh).

Here are charts of the percentage of suitable “small building” per zip codes and the percentage of the electricity needs they could generate per state:

Here’s the kicker: NREL’s study is based on a module efficiency of 16%, but if module efficiency keeps increasing, and several higher solar modules are currently at 20% and going up, the total will go up accordingly.

But deployment is still the main issue. SolarCity used the data collected by NREL to illustrate the current deployment of residential solar versus what it could be based on NREL’s study. Each little square represents enough residential solar to power ~80,000 homes:

As you can see, there’s still a long way to go. There are still a lot of rooftops out there that could benefit from solar installations.

If you want to install a solar array at your home or business, we recommend getting quotes from more than one installer in your region. You can see if it makes sense for your property and if you can be saving money on your energy bill with a free solar quote here.

Here’s the study in full: